Waste oil combustion apparatus

ABSTRACT

A waste oil combustion apparatus can use various kinds of waste oils and burn the same efficiently, and permits effective utilization of the thermal energy resulting from the combustion thereof. The apparatus includes a bottomed cylindrical combustion furnace, a waste oil supply unit for supplying waste oil into the furnace, an auxiliary-fuel supply unit for supplying auxiliary fuel for burning the waste oil in the furnace, an ignition burner for heating the furnace inside and the waste oil and auxiliary fuel to ignite the fuels, an air supply unit for supplying air to the furnace, and a controller for controlling each of the igniting burner, waste oil supply unit, auxiliary-fuel supply unit and air supply unit to act at a predetermined time and operate for a predetermined time. The waste oil is spirally swirled inside the furnace under the action of air from the air supply unit.

CROSS REFERENCE TO RELATED APPLICATION

The present invention contains subject matter related to Japanese PatentApplication JP 2007-52837 filed in the Japanese Patent Office on Mar. 2,2007, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a combustion apparatus using waste oilssuch as discarded lubricant, engine oil or the like as main fuel.

Recently, the regulations on the industrial wastes have been tightenedmore and more. Large costs have been required for disposal of the wasteoils including discarded animal oils such as beef tallow, vegetable oilssuch as soy-beam oil or mineral oils such as lubricant, insulation oil,engine oil, etc. Under these circumstances, it has been proposed toutilize such waste oils as fuel for combustion apparatuses such as aboiler, burner, etc.

However, used soy-beam oil, which is a vegetable oil, for example, has ahigh ignition point and is not easy to burn since it contains impuritiesin volume. To solve this problem, a combustion apparatus using wasteoils as auxiliary fuel has been proposed in Japanese PublishedUnexamined Patent Application No. H08-334220 (Patent Document 1). Insuch combustion apparatuses using waste oils as fuel, impuritiescontained in the oil cause carbon sludge to adhere to the inner wall ofthe combustion furnace or chamber, which leads to hard work for removingthe carbon sludge.

The combustion apparatus disclosed in Patent Document 1 uses kerosene asmain fuel and waste oil as auxiliary fuel. However, this apparatusshould be able to burn waste oils more efficiently.

SUMMARY OF THE INVENTION

It is therefore desirable to overcome the above-mentioned drawbacks ofthe related art by providing a combustion apparatus using various wasteoils each as main fuel and capable of efficiently burning the waste oiland utilizing the resultant heat energy effectively.

According to an embodiment of the present invention, there is provided awaste oil combustion apparatus including a bottomed cylindricalcombustion furnace, a waste oil supplying means for supplying a wasteoil into the combustion furnace, an auxiliary-fuel supplying means forsupplying an auxiliary fuel for burning the waste oil in the combustionfurnace, an ignition means for heating the combustion furnace inside andthe waste oil and auxiliary fuel to ignite the fuels, an air supplyingmeans for supplying air to the combustion furnace, and a controller forcontrolling each of the ignition means, waste oil supplying means,auxiliary-fuel supplying means and air supplying means to act at apredetermined time and operate for a predetermined time. The waste oilsupplying means supplies the waste oil in such a manner that the latteris spirally swirled inside the combustion furnace under the action ofair supplied from the air supplying means.

The combustion apparatus according to an embodiment of the presentinvention uses waste oils each as main fuel and is capable of burningthe waste oils having been discarded as wastes in the past, whichcontributes to deployment of resources. According to the embodiment ofthe present invention, the waste oil supplying means supplies the wasteoil in such a manner that the latter is spirally swirled inside thecombustion furnace under the action of air supplied from the airsupplying means, whereby the waste oil can be burned with an improvedefficiency.

The foregoing and other features and advantages of the present inventionwill become apparent from the following detailed description ofembodiments of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal-sectional view of a waste oilcombustion apparatus according to an embodiment of the presentinvention;

FIG. 2 is a perspective view, enlarged in scale, of a substantial partof the apparatus shown in FIG. 1;

FIG. 3 explains the flow of fuel and air from the fuel supply pipe inthe intake pipe of the apparatus shown in FIG. 1, in which FIG. 3A is across-sectional view of the combustion furnace and FIG. 3B is alongitudinal-sectional view of the combustion furnace;

FIG. 4 is a sectional view of the intake pipe;

FIG. 5 shows a flow of operations made in the waste oil combustionapparatus shown in FIG. 1;

FIG. 6 is a perspective view of a rotary kiln connected to the waste oilcombustion apparatus;

FIG. 7 is a schematic sectional view taken along the axis of rotation ofthe rotary kiln shown in FIG. 6, connected to the waste oil combustionapparatus;

FIG. 8 is a schematic sectional view taken perpendicularly to the axisof rotation of the rotary kiln connected to the waste oil combustionapparatus; and

FIG. 9 schematically illustrates an inner casing of the rotary kilnconnected to the waste oil combustion apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be described in detailbelow concerning the embodiment thereof with reference to theaccompanying drawings.

As shown in FIG. 1, the waste oil combustion apparatus, generallyindicated with a reference numeral 1, includes an annular combustioncylinder 2, a combustion furnace 3 provided inside the combustioncylinder 2, an ignition burner 4 that heats the inside of the combustionfurnace 3 to ignite the fuel and the like, a waste oil supply unit 5 tosupply waste oil as main fuel into the combustion furnace 3, a kerosenesupply unit 6 to supply kerosene as auxiliary fuel into the combustionfurnace 3, an air supply unit 7 to supply air into the combustioncylinder 2, a duct 8 to supply heat resulted from the combustion of thewaste oil in the combustion furnace 3 to a heat exchanger or the likeconnected to the waste oil combustion apparatus 1 for effectiveutilization of the heat, and a controller 10 to control the operation ofthe entire apparatus.

The combustion cylinder 2 is made of a heat resistant steel plate or thelike. It includes a cylindrical annular portion 2 a, a top plate 2 bthat closes the upper end of the annular portion 2 a, and supportingmembers 2 c provided near the lower end of the annular portion 2 a tosupport the combustion furnace 3. In the combustion cylinder 2, thelower end of the annular portion 2 a serves as a burning port. The duct8 is connected to that lower end to supply the heat of combustion in thecombustion furnace 3 inside the combustion cylinder 2 to the downstream.

As shown in FIG. 2, the annular portion 2 a of the combustion cylinder 2is of a double structure being hollow to have an inner space 11 formedtherein and to which water is supplied. The annular portion 2 a has awater inlet 12 provided on the peripheral surface near the lower end ofthe annular portion 2 a at which the latter is connected to the duct 8,and the water inlet 12 communicates with the inner space 11. The annularportion 2 a has a water outlet 13 provided on the peripheral surfacenear the upper end at which a top plate 2 b is provided, and the wateroutlet 13 communicates with the inner space 11. Also, the annularportion 2 a is connected at the water inlet 12 thereof to a water supplyunit 14. Water supplied from the water supply unit 14 is charged intothe inner space II through the water inlet 12, and it goes out of theinner space 11 through the water outlet 13. In the annular portion 2 a,the water thus filled in the inner space 11 will serve as a coolant thatcools the waste oil combustion apparatus 1. The water supply unit 14 isof a well-known type, for example, a pump.

The top plate 2 b provided at the upper end of the annular portion 2 ais a disc-shaped member that closes the upper end of the annular portion2 a. It has an air inlet 15 connected to a blower 16 and through whichair is supplied into the combustion cylinder 2. The air inlet 15 isformed circular to blow air to between the combustion cylinder 3 and theannular portion 2 a surrounding the former.

The supporting members 2 c support the combustion furnace 3 formed likea footman. More specifically, each of the supporting members 2 c isformed from a bar-shaped member extending from near the lower end of theannular portion 2 a of the combustion cylinder 2 toward the inside ofthe annular portion 2 a. The supporting member 2 c is a little bent atthe free end thereof toward the upper end of the annular portion 2 a.Also, the supporting member 2 c is longitudinally hollow (as indicatedwith a reference numeral 2 d) from one end thereof to the other,allowing air to pass through. The supporting member 2 c is connected atone end thereto to an air blower 9 which is an air source. The airblower 9 is to supply air to the combustion furnace 3. It blows air tothe bottom of the combustion furnace 3 through the inner space 2 d inthe connected supporting member 2 c to cool the combustion furnace 3.

The combustion furnace 3 is made of a heat resistant steel plate or thelike to have the form of a bottomed cylinder. It is placed inside thecombustion cylinder 2. The combustion furnace 3 has formed therein nearan open end 3 a thereof an insertion hole 18 in which there is inserteda supply pipe assembly 17 through which waste oil, kerosene and air aresupplied from the waste oil supply unit 5, kerosene supply unit 6 andair supply unit 7, respectively, to the combustion furnace 3. Thecombustion furnace 3 has a bottom 3 b on which there will be receivedthe mist, not completely burned, of the fuels including the waste oilsprayed from the supply pipe assembly 17. The fuels, including the wasteoil on the bottom 3 b of the combustion furnace 3, are heated in thecombustion furnace 3 for vaporization and burning.

The ignition burner 4 is connected to the supply pipe assembly 17. Ituses kerosene, for example. The ignition burner 4 heats the inside ofthe combustion furnace 3 to ignite waste oil so that the waste oilcombustion apparatus 1 can start combustion or other operation with onlythe waste oil. It should be noted that the ignition burner 4 is notlimited to the above-mentioned type using kerosene but may be of a typeusing gas or the like.

The waste oil supply unit 5 includes a first waste oil tank 19 in whichwaste oil is stored, a second waste oil tank 20 to which the waste oilis supplied from the first waste oil tank 19, a heater 21 providedinside the second waste oil tank 20 to heat the waste oil in the secondwaste oil tank 20, a waste oil supply pipe 22 through which the wasteoil is supplied from the second waste oil tank 20 into the combustionfurnace 3, a waste oil pressure regulator 23 provided in the waste oilsupply pipe 22 to regulate the pressure of the waste oil supplied fromthe second waste oil tank 20, and a waste oil supply/stop valve 24 tosupply or stop the waste oil to the combustion furnace 3.

The first waste oil tank 19 stores waste oil as main fuel for use withthe waste oil combustion apparatus 1. The second waste oil tank 20 issupplied with the waste oil from the first waste oil tank 19. Using aliquid level adjuster (not shown) including a float and needle, thesecond waste oil tank 20 stores the waste oil supplied from the firstwaste oil tank 19 under a constant pressure. Inside the second waste oiltank 20, there is provided a heater 21 that heats the waste oil in thetank to lower the viscosity of the waste oil. The heater 21 is of awell-known type, and its operation is controlled by the controller 10.Water is supplied to the inner space 11 of the combustion cylinder 2 andgiven the heat of combustion in the combustion furnace 3. The water thusheated is circulated through the water outlet 13 to the second waste oiltank 20 in which it further heats the waste oil being heated by theheater 21. At this time, the controller 10 makes a selection between theheat exchange by the discharged hot water from the combustion cylinder 2and the operation of the heater 21 in response to the operational statusof the combustion furnace 3.

Note that for a lower viscosity of the waste oil in the second waste oiltank 20, the latter may not be arranged to be supplied with the hotwater from the combustion cylinder 2 as described above but may beprovided in a position where it itself can be given the radiant heatfrom the combustion furnace 3.

The waste oil supply pipe 22 is connected to a fuel supply tube 29(shown in FIG. 4), which will further be described later, in the supplypipe assembly 17 to supply the waste oil from the second waste oil tank20 to the combustion furnace 3. The waste oil pressure regulator 23 isprovided in the waste oil supply pipe 22 to regulate the pressure of thewaste oil being supplied from the second waste oil tank 20 to the supplypipe assembly 17. The waste oil pressure regulator 23 is controlled bythe controller 10 to regulate the pressure of the waste oil beingsupplied. The waste oil supply/stop valve 24 is provided in the wasteoil supply pipe 22 and downstream of the waste oil pressure regulator 23to adjust the supply of the waste oil from the second waste oil tank 20.Similarly to the waste oil pressure regulator 23, the waste oilsupply/stop valve 24 is operated (opened or closed) under the control ofthe controller 10.

Note that the waste oil pressure regulator 23 and waste oil supply/stopvalve 24 may not be arranged separately from each other as above butthey may be of an integral structure capable of adjusting the supply ofthe waste oil through the waste oil supply pipe 22 and regulating thepressure of the waste oil in the waste oil supply pipe 22.

The kerosene supply unit 6 includes a kerosene tank 25 in which keroseneas auxiliary fuel is stored, a kerosene supply pipe 26 to supplykerosene from the kerosene tank 25 into the combustion furnace 3, akerosene pressure regulator 27 provided in the kerosene supply pipe 26to regulate the pressure of the kerosene supplied from the kerosene tank25, and a kerosene supply/stop valve 28 to supply or stop the keroseneto the combustion furnace 3.

The kerosene tank 25 stores kerosene as auxiliary fuel for the waste oilcombustion apparatus 1. The kerosene supply pipe 26 is connected to thefuel supply tube 29, which will further be described later, in thesupply pipe assembly 17 to supply the kerosene from the kerosene tank 25to the combustion furnace 3. The kerosene pressure regulator 27 isprovided in the kerosene supply pipe 26 to regulate the pressure of thekerosene being supplied from the kerosene tank 25 to the supply pipeassembly 17. The kerosene pressure regulator 27 is controlled by thecontroller 10 to regulate the pressure of the kerosene being supplied.The kerosene supply/stop valve 28 is provided in the kerosene supplypipe 26 and downstream of the kerosene pressure regulator 27 to adjustthe supply of the kerosene from the kerosene tank 25. Similarly to thekerosene pressure regulator 27, the kerosene supply/stop valve 28 isoperated (opened or closed) under the control of the controller 10.

Note that the kerosene pressure regulator 27 and kerosene supply/stopvalve 28 may not be arranged separately from each other as above butthey may be of an integral structure capable of adjusting the supply ofthe kerosene through the kerosene supply pipe 26 and regulating thepressure of the kerosene in the kerosene supply pipe 26.

As shown in FIGS. 3 and 4, the supply pipe assembly 17 includes a fuelsupply pipe 29 to which the waste oil supply pipe 22 and kerosene supplypipe 26 are connected, an air supply pipe 30 having the fuel supply pipe29 provided therein and which is supplied with air from the air supplyunit 7, and a heat shielding plate 31 provided to cover a portion, nearthe free end, of the air supply pipe 30. The supply pipe assembly 17 isinserted in the insertion hole 18 provided near the open end of thecombustion furnace 3 as shown in FIG. 3 to supply fuel (waste oil andkerosene) and air into the combustion furnace 3.

The insertion hole 18 is to have the supply pipe assembly 17 insertedthrough it as above. It is formed so that the supply pipe assembly 17 isheld tangentially to the inner circumference of the combustion furnace 3as shown in FIG. 3A (cross-sectional view) and obliquely from abovetoward the bottom 3 b of the combustion furnace 3 as will be seen inFIG. 3B (longitudinal-sectional view). This geometry is intended toswirl the fuel and air supplied from the supply pipe assembly 17 forefficient burning.

The fuel supply pipe 29 is connected to the waste oil supply pipe 22 andkerosene supply tube 26 to supply waste oil and kerosene into thecombustion furnace 3. It is connected at one end thereof to the wasteoil supply pipe 22 and kerosene supply pipe 26 to supply waste oil andkerosene as fuels into the combustion furnace 3, and projected at theother end thereof into the combustion furnace 3.

The air supply pipe 30 is larger in inside diameter than the fuel supplypipe 29 and is laid coaxially with the latter. The air supply pipe 30 isconnected at one end thereof to the air supply unit 7 and projected atthe other end into the combustion furnace 3. The air supply pipe 30supplies air from the air supply unit 7 into the combustion furnace 3.Also, the end, projected into the combustion furnace 3, of the airsupply pipe 30, is deeper in the combustion furnace 3 than thecorresponding end of the fuel supply pipe 29. The free end, projectedinto the combustion furnace 3, of the air supply pipe 30, is somewhatreduced in inside diameter (as indicated with a reference numeral 30 a).The smaller-diameter end 30 a forms a Venturi tube that elevates theflow rate of supplied air to atomize waste oil etc. supplied from thefuel supply pipe 29 for spraying into the combustion furnace 3.

The heat shielding plate 31 covers the near free-end portion of the airsupply pipe 30 to shield heat from the combustion furnace 3 in order toprevent the air supply pipe 30 from being overheated. The heat shieldingplate 31 has an ignition hole 32 through which flame is taken in fromthe ignition burner 4.

The ignition hole 32 is provided in such a position near the endportion, inside the combustion furnace 3, of the heat shielding plate 31that fuel from the fuel supply pipe 29 can be ignited by the flame fromthe ignition burner 4.

The air supply unit 7 is a blower connected to the air supply pipe 30 tosupply combustion air into the combustion furnace 3 and to atomize wasteoil from the fuel supply pipe 29 for spraying into the combustionfurnace 3.

The duct 8 is to supply the heat of combustion developed in thecombustion furnace 3 to a drying equipment which is located downstreamof the waste oil combustion apparatus 1. The duct 8 is annular andgenerally equal in diameter to the combustion cylinder 2. It is bent forone and other ends thereof to form an angle of about 90 degrees betweenthem. As shown, the duct 8 is of a double structure being hollow to havean inner space 33 formed therein as in the combustion cylinder 2 and towhich water is supplied.

The duct 8 is connected at one end thereof to the bottom of thecombustion cylinder 2 and at the other end to a rotary kiln 41 whichwill be described in detail later. Further, the duct 8 has a water inlet34 provided at the peripheral surface thereof near the end at which itis connected to the rotary kiln 41 and which communicates with the innerspace 33, and a water outlet 35 provided at the peripheral surfacethereof near the end at which it is connected to the combustion cylinder2 and which communicates with the inner space 33. The duct 8 isconnected at the water inlet 34 thereof to a water supply unit 36 sothat water is taken into the inner space 33 and discharged from thewater outlet 35. The water thus filled in the inner space 33 of the duct8 serves as a coolant to cool the waste oil combustion apparatus 1. Thewater supply unit 36 is of a well-known type, for example, a pump.

Note that the water supply unit 36 that supplies water to the innerspace 33 of the duct 8 may not be provided separately from the watersupply unit 14 that supplies water to the inner space 11 of thecombustion cylinder 2 as above but a single water supply unit may beused to supply water to the inner spaces 33 and 11.

The controller 10 is to control the operation of the entire waste oilcombustion apparatus 1. More specifically, the controller 10 controlsthe supply rate and pressure of water oil from the waste oil supply unit5, those of kerosene from the kerosene supply unit 6, and supply rateetc. of air from the air supply unit 7. The controller 10 includes a CPU(central processing unit), a memory and a timer, which are connected toeach other via a bus or the like. The memory in the controller 10 hasstored therein an operation timing program for each unit. The timer inthe controller 10 counts a start time of each operation. CPU in thecontroller 10 counts a time count supplied from the timer, and controlsthe operation of each unit according to a corresponding program evokedfrom the memory. The controller 10 is connected to the ignition burner4, waste oil supply unit 5, kerosene supply unit 6, air supply unit 7,air blower 9, water supply units 14 and 36, blower 16, etc. and controlsoutputs from these units.

Next, the operation for combustion of waste oil in the waste oilcombustion apparatus 1 constructed as having been explained above willbe explained with reference to FIG. 5. As shown, in step S1, the userturns on the power supply to -the waste oil combustion apparatus 1. Instep S2, the controller 10 puts, into operation, the ignition burner 4,waste oil supply unit 5, kerosene supply unit 6, air supply unit 7 andblower 16. Then, waste oil, kerosene and air supplied to the combustionfurnace 3 are burned while being swirled down spirally along the innersurface of the combustion furnace 3 toward the bottom 3 b and thenswirled up from the bottom 3 b toward the open end of the combustionfurnace 3 as shown in FIG 3.

In step S3 the controller 10 determines whether a predetermined time,for example, five minutes, has elapsed after each unit is put intooperation in step S2. If the controller 10 has decided in step S3 thatthe predetermined time has not elapsed, it will repeat the operation instep S3. In case the controller 10 has decided that the predeterminedtime has elapsed, it will go to step S4. Each unit is operated for thepredetermined time in step S3 in order to heat the inside the combustionfurnace 3 by the ignition burner 4 to produce an atmosphere for easycombustion of the waste oil.

Next, in step S4, the controller 10 controls the kerosene supply unit 6to stop the supply of kerosene and the ignition burner 4, to stop theoperation. At this time, the controller 10 controls the waste oil supplyunit 5 and air supply unit 7 to keep operating.

Thus, in the waste oil combustion apparatus 1, waste oil and air aresupplied from the waste oil supply unit 5 and air supply unit 7,respectively, into the combustion furnace 3 so that only the waste oilwill be burned as fuel. At this time, the waste oil, kerosene and airsupplied from the supply pipe assembly 17 into the combustion furnace 3of the waste oil combustion apparatus 1 are swirled down along the innersurface of the combustion furnace 3 toward the bottom 3 b of the furnace3 and then swirled up from the bottom 3 b, which will assure efficientand stable combustion of the waste oil. Also, since the waste oilcombustion apparatus 1 is so arranged that after elapse of thepredetermined time, supply of the kerosene is stopped for combustion ofthe waste oil alone. Thus, it is possible to limit the consumption ofthe kerosene. Further in the waste oil combustion apparatus 1, theblower 16 blows air into the space between the combustion cylinder 2 andcombustion furnace 3 from the upper end toward lower end of thecombustion cylinder 2 to guide the heat of combustion and flame in thecombustion furnace 3 into the duct 8 (as indicated with a referencesymbol A in FIG. 1).

In the waste oil combustion apparatus 1, with the fuels and air beingsupplied into the combustion furnace 3 from the supply pipe assembly 17provided at a predetermined angle in relation to the combustion furnace3, the waste oil can be burned more efficiently and positively. Also,since during operation of the waste oil combustion apparatus 1, namely,during combustion of the waste oil, the combustion furnace 3, combustioncylinder 2, duct 8, etc. are cooled while the air blower 9 and watersupply units 14 and 36 are in operation, the durability of the entireapparatus is much improved. Further, since the controller 10 of thewaste oil combustion apparatus 1 can lower the viscosity of the wasteoil by controlling the operation of the heater 21 of the waste oilsupply unit 5, it is possible to assure efficient and positivecombustion of the waste oil.

Moreover in the waste oil combustion apparatus 1, since it is possibleto burn the waste oil efficiently and stably, the heat of combustion canbe utilized for various purposes.

For one of such purposes, the rotary kiln 41 may be connected to thedownstream of the waste oil combustion apparatus 1 having been explainedabove, namely, to the end of the duct 8 to build a drying system formetal chips resulted from machining. This drying system can effectivelyutilize waste oil to dry the metal chips for recycling.

The rotary kiln connected to the waste oil combustion apparatus 1 willbe explained below with reference to the accompanying drawings. In therotary kiln 41, metal chips 44 resulted from machining, fed from on abelt conveyor 42 into a feeding hopper 43, are guided by means of aspiral conveyor 45 into a rotary kiln body 51, and then heated with hotair introduced into an outer casing 56 of the rotary kiln body 51 froman end of the latter opposite to the feeding hopper 43 of the rotarykiln body 51, as shown in FIG. 6. The rotary kiln 41 includes a supportbase 52, a rotary kiln body 51 supported on the support base 52 by meansof support rollers 53 provided on the support base 52, and a motor 54 torotate the rotary kiln body 51.

The support base 52 is made of a heat resistant steel plate or the like.The plurality of support rollers 53, motor 54, etc. are fixed in placeon the top of the support base 52. It supports the rotary kiln body 51on contact with the support rollers 53.

The support rollers 53 on the support base 52 are to support the rotarykiln body 51 rotatably. For example, four support rollers 53 may beprovided on the support base 52.

The rotary kiln body 51 rotatably supported on the support rollers 53 isof a double structure including the outer casing 56 and an inner casing55 provided in the outer casing 56 as shown in FIGS. 6 to 8.

The inner casing 55 of the rotary kiln body 51 is made of heat resistantsteel or the like to be generally cylindrical. At one end 55 a of theinner casing 55, there is provided the spiral conveyor 45 into whichmetal chips 44 to be dried are put. The inner casing 55 is supplied atthe other end 55 b thereof with the heat of combustion from the wasteoil combustion apparatus 1. Also, the inner casing 55 has provided onthe inner surface 55 c thereof a plurality of first feed vanes 57 thatmove the metal chips 44 fed from the spiral conveyor 45 in a directionfrom the one end 55 a to the other end 55 b as shown in FIGS. 7 to 9.

The first feed vanes 57 are provided intermittently on the inner surface55 c of the inner casing 55 to project inwardly of the latter and depicta virtual spiral extending from the one end 55 a toward the other end 55b. The first feed vanes 57 are fixed obliquely in a direction in whichrotation of the inner casing 55 converts circumferential motion intoaxial motion The inner casing 55 is rotated along with the outer casing56, so that the first feed vanes 57 move the metal chips 44 put in theinner casing 55 in a direction from the one end 55 a to the other end 55b while shaking them The first feed vanes 57 are intermittently disposedin order to forward the heat of combustion supplied from the waste oilcombustion apparatus 1 in a direction toward the one end 55 a of theinner casing 55.

The outer casing 56 having the inner casing 55 provided therein made ofa heat resistant steel plate or the like to be generally cylindrical.The outer casing 56 is large enough in diameter to house the innercasing 55, and provided concentrically with the inner casing 55. One end56 a of the outer casing 56 is opposite to the one end 56 a. As shown inFIG. 2, the outer casing 56 has provided on the inner surface 56 cthereof a plurality of second feed vanes 58 that take in the heat ofcombustion from the waste oil combustion apparatus 1 and move, to theother end 56 b of the outer casing 56, the metal chips 44 which are tobe passed from the other end 55 b of the inner casing 55 to the otherend 56 b of the outer casing 56.

The second feed vanes 58 are provided intermittently on the innersurface 56 c of the outer casing 56 to project inwardly of the latterand depict a virtual spiral extending from the one end 56 a toward theother end 56 b. The second feed vanes 58 are fixed obliquely in adirection in which rotation of the outer casing 56 convertscircumferential motion into axial motion The second feed vanes 58 aredirected crosswise in relation to the first feed vanes 57. The outercasing 56 is rotated along with the inner casing 55 to move, by thesecond feed vanes 58, the metal chips 44 transferred from the innercasing 55 in a direction from the other end 56 b to the one end 56 awhile shaking them. Similarly to the first feed vanes 57, the secondfeed vanes 58 are intermittently disposed in order to forward the heatof combustion supplied from the waste oil combustion apparatus 1 in adirection toward the one end 56 a of the outer casing 56. The outercasing 56 further has provided on the outer surface 56 d thereof rings59 which are received on the support rollers 53, and a transmissionmember 61 that transmits the driving force from the motor 54 to therotary kiln body 51 through a change belt 60.

The rings 59 are positioned on the outer surface 56 d of the outercasing 56 for engagement on the support rollers 53. The transmissionmember 61 is annular to extend over the outer surface 56 d of the outercasing 56, and positioned to face the motor 54. It is a kind of rack,for example, which is in mesh with the chain belt 60.

The rotary kiln body 51, having the double structure including the innerand outer casings 55 and 56 as above, is coupled by a coupling member 62to each other to be concentric with each other. The coupling member 62is to couple the inner and outer casings 55 and 56 securely to eachother at the one end 55 a, for example, of the inner casing 55, wherebyrotation of the outer casing 56 by the motor 54 leads to similarrotation of the inner casing 55. In the rotary kiln body 51, since thedirection of the first feed vanes 57 spirally provided in the innercasing 55 is different from that of the second feed vanes 58 alsospirally provided in the outer casing 56, the metal chips 44 in theinner casing 55 and those in the outer casing 56 can be moved indifferent directions with the inner and outer casings 55 and 56 beingrotated in the same direction

Note that the coupling member 62 may not be provided in a limited placesuch as the one end 55 a of the inner casing 55 but may take any form ormay be provided in more than one place so long as it can securely couplethe inner and outer casings 55 and 56 to each other so that they areconcentric with each other.

The spiral conveyor 45 to feed the to-be-dried metal chips 44 to the oneend 55 a of the inner casing 55 is generally cylindrical. It hasprovided therein a vane 63 that moves the supplied metal chips 44. Thespiral conveyor 45 has connected thereto a motor 64 that rotates thevane 63. The spiral conveyor 45 has the feeding hopper 43 installed atone end 45 a thereof, and is inserted at the other end 45 b thereof inthe one end 55 a of the inner casing 55. The vane 63 of the spiralconveyor 45 extends spirally to move the metal chips 44 from the one end45 a toward the other end 45 b.

Note that the spiral conveyor 45 may not be constructed as above but maybe of any structure so long as it can move the metal chips 44 into theinner casing 55.

The feeding hopper 43 installed to the spiral conveyor 45 is to feed themetal chips 44 to the spiral conveyor 45. The feeding hopper 43 has, forexample, a vibrator etc. (not shown) and feeds a predetermined amount ofthe metal chips 44 to the spiral conveyor 45 under the effect ofvibration given by the vibrator.

The rotary kiln 41 further has a blower 65 for cooling the surface ofthe rotary kiln body 51, that is, the outer surface 56 d of the outercasing 56, and a blower 66 for cooling the metal ships 44 already driedand going to be discharged from the rotary kiln body 51 at the one end56 a of the outer casing 56 while forwarding the heat of combustion fromthe waste oil combustion apparatus 1 into the rotary kiln body 51. Therotary kiln 41 also has provided at the one end 56 a of the outer casing56 a duct 67 which guides air from the blower 66.

In the rotary kiln 41 constructed as above, the motor 54 is driven torotate the rotary kiln body 51 and take in the heat of combustion fromthe waste oil combustion apparatus 1 into the rotary kiln body 51 fromthe other end 56 b of the outer casing 56. In this condition, the metalchips 44 are fed by the spiral conveyor 45 from the one end 55 a of theinner casing 55, and shaken and moved by the first feed vanes 57 fromthe one end 55 a to the other end 55 b while being heated. At the otherend 55 b of the inner casing 55, the metal chips 44 take a position nearthe waste oil combustion apparatus 1 which is a heat source, and thusdried and transferred to the other end 56 b of the outer casing 56.Further, the metal chips 44 are shaken and moved by the second feedvanes 58 from the other end 56 b to one end 56 a of the outer casing 56.That is, they are moved away from the waste oil combustion apparatus 1which is the heat source, while gradually releasing the heat. Finally,the metal chips 44 thus heated and dried are discharged from the one end56 a of the outer casing 56.

In the above rotary kiln 41, since the metal chips 44 are dried in bothforward and backward ways, the rotary kiln body 51 can be designedshorter in whole length. Therefore, the rotary kiln 41 can be formedsmaller. The reduction in whole length of the rotary kiln body 51 of therotary kiln 41 permits to have the waste oil combustion apparatus 1operate with a lower output. Further, in the rotary kiln 41, since thefirst and second feed vanes 57 and 58 are provided intermittently todepict a virtual spiral, arrival of the heat of combustion from thewaste oil combustion apparatus 1 at the one ends 55 a and 56 a of theinner and outer casings 55 and 56, respectively, can be controlledappropriately to prevent the temperature from being sharply elevated ina position near the other end 55 b.

Moreover, since the inner and outer casings 55 and 56 of the rotary kiln41 are coupled to each other by the coupling member 62, they can berotated by a single motor 54, which contributes to power saving.

Also, a drying apparatus including the waste oil combustion apparatus 1and rotary kiln 41 connected to each can use waste oil as main fuel todry the metal chips 44. Namely, the embodiment of the present inventionpermits more effective use of resources and space saving.

Note that the first and second feed vanes 57 and 58 are not limited tothe aforementioned ones but the feed vanes may be designed to have avariable tilt angle, height, etc. in the axial direction for moving themetal chips axially at a variable speed corresponding to the uniformrotation of the rotary kiln body 51. More specifically, the first feedvanes 57 are designed to have an increased height and tilt angle at theone end 55 a for moving the metal chips 44 toward the other end 55 b atan increased speed, while having a decreased height and tilt angle atthe other end 55 b for having the metal chips 44 stay for a longer timeto be long exposed to the heat of combustion from the waste oilcombustion apparatus 1.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A waste oil combustion apparatus comprising: a bottomed cylindricalcombustion furnace; a waste oil supplying means for supplying a wasteoil into the combustion furnace; an auxiliary-fuel supplying means forsupplying an auxiliary fuel for burning the waste oil in the combustionfurnace; an ignition means for heating the combustion furnace inside andthe waste oil and auxiliary fuel to ignite the fuels; an air supplyingmeans for supplying air to the combustion furnace; and a controller forcontrolling each of the igniting means, waste oil supplying means,auxiliary-fuel supplying means and air supplying means to act at apredetermined time and operate for a predetermined time, the waste oilsupplying means supplying the waste oil in such a manner that the latteris spirally swirled inside the combustion furnace under the action ofair supplied from the air supplying means.
 2. The waste oil combustionapparatus according to claim 1, wherein the waste oil supply means andair supplying means supply the waste oil and air, respectively, fromnear an open end of the combustion furnace in such a manner that thewaste oil and air are spirally swirled down along the inner surface ofthe combustion furnace toward the bottom of the combustion furnace. 3.The waste oil combustion apparatus according to claim 1, wherein thewaste oil supplying means further includes a pressure regulator forsupplying the waste oil into the combustion furnace under apredetermined pressure, and a heater that uses the heat of combustionfrom the combustion furnace to heat the waste oil.
 4. The waste oilcombustion apparatus according to claim 2, wherein the waste oilsupplying means further includes a pressure regulator for supplying thewaste oil into the combustion furnace under a predetermined pressure,and a heater that uses the heat of combustion from the combustionfurnace to heat the waste oil.